Stray electrical energy is often identified as “stray voltage.” Stray voltages describe voltages that exist between two objects that should not have a voltage difference between them. Stray voltages may be produced, for example, by improper grounding of electrical equipment, unbalanced multi-phase electrical equipment such as motors, generators, and transformers, or defective equipment. Electrical devices typically include a ground wire which is often connected to a metal rod, water pipe, or other conductive member extending into the ground. Ideally, the ground conductor remains at a zero voltage potential. However, if any of the above-mentioned conditions exist, there is the possibility of a voltage potential existing on the ground conductor and being passed into the ground.
Stray electrical energy may also be identified as “leakage current.” Leakage currents exist, for example, when current unexpectedly flows along an unintended conductive path. Deterioration or failure of an electrical device may create the unintended conduction. Alternately, electromagnetic coupling of radiated energy may establish current flow in electrical conductors. Unintended conduction also occurs, for example, due to non-ideal behavior of electrical components such as diodes, transistors, and capacitors.
The modern farm presents one environment in which stray electrical energy is of interest. Farms typically require a significant amount of electrical equipment, such as ventilation fans, water pumps, and specialized equipment, for example, milking machines on dairy farms. The electrical equipment may be spread out across several buildings and is often present in a dirty and wet environment. The harsh environment has the potential for excessive wear, corrosion, and/or failure of the electrical equipment. Prior to failure of electrical equipment, the equipment may operate in a state which introduces stray voltage and/or leakage currents onto ground conductors.
Although the stray electrical energy is typically imperceptible to humans or animals, it is possible that stray electrical energy of sufficient amplitude may exist to be felt by or cause irritation to humans or to the animals. Stray electrical energy may travel between buildings and aggregate from multiple buildings to create a potentially unsafe or unpleasant environment. For example, animal water tanks are often metallic. Further, the water tanks may be fed by water pumped from a central source or from a well and carried through metal pipes. Stray electrical energy may be conducted through the water, pumps, pipes, water tanks, or a combination thereof into the animals. The effects of the stray electrical energy on animals have been reported to range from a minor irritation to causing sickness or death of an animal. Accurate measuring and recording of stray electrical energy can help in mitigating this energy.
Typically, stray electrical energy is monitored by measuring stray voltage. Stray voltages on farms have typically been measured at specific points using a voltmeter with a 500 ohm resistor in parallel to the leads from the voltmeter. A first lead is then connected to, or inserted into, the ground and a second lead is connected to the point at which the stray voltage is to be measured, such as a water tank, metal pipe, or metal structural element. The 500 ohm resistance is selected as it is believed to simulate the resistance through a cow's body.
However, measuring stray voltage in this manner is not without its drawbacks. Readings of stray voltage are typically taken at a single point. The reading may be affected by many variables, including loading of the electrical system or humidity. Further, the single reading captures the stray voltage at only a single instant and fails to capture trends or peak values of the stray voltage. Additionally, measurements of leakage current may provide more relevant information about the level of stray electrical energy present than measurements of stray voltage. A high level of voltage with a low current, may present little danger, while a relatively low level of voltage with a high current may present a significant danger.
Therefore, it is a primary object and feature of the present invention to provide an improved method of measuring and recording stray electrical energy, especially over a significant geographical region, to identify areas of interest having higher levels of stray voltage and/or leakage current and to minimize the level of stray electrical energy in the identified areas.
In accordance with the present invention, a system for reducing stray electrical energy over a geographical region includes a plurality of sensing devices positioned within the geographical region, a data acquisition device, and at least one stray electrical energy mitigation device. Each sensing device includes a sensor generating a signal corresponding to the amplitude of stray electrical energy present at a location of the sensing device, and a communication port transmitting the signal. The data acquisition device includes at least one input configured to receive the signals from the sensing devices, and at least one memory device configured to store the signals from the sensing devices. A processor is configured to execute a stored program to compile the signals over the geographical region for a preselected time period, which may be 6 months or longer, and to identify at least one pattern of emission of the stray electrical energy over the period of time. At least one stray electrical energy mitigation device is positioned within the geographical region as a function of the pattern of emission of the stray electrical energy. The at least one stray electrical energy mitigation device may be selected from a dual holding tank system connected in series with a supply line, a multi-layer, electrically isolated supply line, a pump connected in series with the supply line to modify water flow between a water supply and a water tank, and an electrical insulator positioned between the water tank and a surface on which the tank is placed.
In accordance with another aspect of the present invention, at least one of the signals corresponding to the amplitude of stray electrical energy measures the amplitude of a leakage current at a resolution finer than 30 milliamps. Optionally, the resolution is selected between 50 microamps and 1 milliamp.
In accordance with yet another aspect of the present invention, multiple sensing devices positioned within the geographical region generate signals corresponding to an environmental condition within the geographical region, and the data acquisition device stores each of the plurality of signals corresponding to the environmental condition in the memory device over the period of time. The processor is further configured to execute the stored program to correlate the pattern of the emission of stray electrical energy to the signals corresponding to the environmental condition.
In accordance with another embodiment of the present invention, an animal watering system with improved electrical isolation includes a water supply, a supply line in fluid communication with the water supply, a water tank configured to deliver water to at least one animal and in fluid communication with the supply line, and at least one electrical isolation means operatively located proximate to one of the water supply, the supply line, and the water tank to mitigate stray electrical energy. The electrical isolation means may further include a fill valve having an input in fluid communication with the supply line and an output in fluid communication with a first holding tank. The first holding tank is operatively connected to the output of the fill valve, and the fill valve selectively establishes fluid communication between the supply line and the first holding tank. A coupling valve has an input operatively connected to the first holding tank and an output operatively connected to a second holding tank. The coupling valve selectively establishes fluid communication between the first holding tank and the second holding tank. An exit valve has an input operatively connected to the second holding tank and an output in fluid communication with the water tank. The exit valve selectively establishes fluid communication between the second holding tank and the water tank. The animal watering system may further include a first gasket positioned between the coupling valve and either the first holding tank and the second holding tank. The animal watering system may similarly include a second gasket positioned between the coupling valve and the other holding tank. Each of the gaskets is made of a non-conductive material.
In accordance with another aspect of the invention, the animal watering system also includes a data acquisition device and multiple sensing devices positioned within the geographical region. The data acquisition device includes at least one memory device configured to receive a plurality of signals corresponding to an amplitude of stray electrical energy and a processor configured to execute a stored program. Each sensing device includes a sensor generating one of the signals corresponding to the amplitude of stray electrical energy present at a location of the sensing device and a communication port transmitting the signal to the data acquisition device. The processor executes to compile the signals over the geographical region for a preselected time period, and the electrical isolation means is selected as a function of the compiled signals
In accordance with still another aspect of the invention, the electrical isolation means may be a supply line with multilayer construction. The multilayer construction includes an internal pipe having an inner periphery and an outer periphery, an electrically conductive layer adjacent to the outer periphery of the internal pipe, and an external layer substantially covering the electrically conductive layer. The electrical isolation means may also include a pump connected in series with the supply line to periodically interrupt the water flow and inject an air pocket in the supply line. Optionally, the electrical isolation means may further include a nozzle operatively connected between an output of the supply line and the water tank.
In accordance with yet another embodiment of the present invention, a method of monitoring stray electrical energy over a plurality of locations obtains signals corresponding to an amplitude of stray electrical energy at a plurality of locations with a sensing device. The signals are transmitted from each of the plurality of locations to a data acquisition device, and analyzed to identify at least one pattern of stray electrical energy. The stray electrical energy is mitigated as a function of the pattern of stray electrical energy.
These and other objects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.